This invention relates to monostable circuits, and more particularly, to such circuits which are self-latching and have a pulse width which is controllable.
A monostable circuit is a fairly general purpose circuit used in various electronic environments. It is commonly used as a timing circuit and is available in a lower performance version referred to as a 555 timer circuit. That circuit is a TTL based circuit which also comes in a CMOS version and is used for timing or simply turning on other circuits. Those circuits require the addition of a resistor and capacitor to define the circuit timing. The shortest pulse which can typically be produced is approximately one microsecond.
The preferred embodiment of the present invention is intended for use specifically in an oscilloscope for such functions as glitch triggering, glitch filtering, slew rate detection and metatransition triggering. It is intended to be used to discriminate pulses to determine whether an input signal has a pulse width greater than or less than a predetermined amount. However, unlike conventional monostable circuits, it was necessary to develop one which would be functional at the level of up to 500 MHz sample rate in the 400 to 500 picosecond pulse width range.
Such a circuit could also be used for other things, such as setting up the pulse width on an external clock or to provide probe timing skewing where the clocks in a digital oscilloscope would be delayed in order to compensate for differences in probe length. It will be understood that there are also other applications for such a circuit.
These functions may also be provided by the use of a substantial number of flip flops to count timing or the use of very involved circuitry having a very large number of transistors.